Moscow University
Anthropology
Bulletin
Anthropology
Bulletin
Department of Biological Evolution, Biological Faculty, MSU, Moscow
Severtsov A.S., e-mail: asevertsov@yandex.ru
In vertebrate populations, physiological and ethological traits are the main subjects to natural selection. In general, these traits possess wide norm of reaction and low hereditability. The main causes of elimination in vertebrate population are: predators, parasites, infections and an influence of harsh abiotic factors joined with the deficiency of environmental resources. Competition severely affects physiological state of animals and, in that way, places them under an exposure to eliminating factors. Population undergoes an additive influence of the combination of environmental factors, which compose the ecological niche of a species. As a result of this influence, most part of the individuals dies. In general, population number is much higher than the number of its breeding part. The strength of natural selection is usually very high. However, selection has no evolutionary effect because of its multiple oppositely directed vectors, which constrain each other. The combination of these vectors constitutes the balance of selection forces impeding the evolution of phenotypic traits. Low level of hereditability of phenotypic trait is an additional cause of the slowness of the trait evolution. The rate of evolution increases during the ecological crises: extinction of populations leads to release of environmental resources, breaking the balance of selection forces and appearance of new directions of natural selection. On the contrary, in the stable ecosystems evolution proceeds at a very low rate and leads to increase in the level of interspecies co-adaptation. Any advantages in fitness acquiring by one of the species stimulate evolutionary changes in all co-adapted species. However, high level of co-adaptation impedes subsequent adaptive changes. Shifts of environmental conditions cause the transient misbalance of selective forces and selection for the adaptation to oscillating factors. This level of adaptation seems to be redundant in normal conditions, but provides survival of population in extreme ones. The increase in the level of eurybiotic capacity (possibility to utilize wide range of forage resources or inhabit many different biotopes etc.) is one of the most effective ways to increase species stability. High level of eurybiotic capacity implies low dependence on the ecological niche. In this case, intraspecific relationships become the main subject of natural selection. In birds and mammals, they are based on the behavior. Reproductive success in these animals in many respects depends on their behavioral adaptations. Selection leads to appearance of more complex behavioral traits and improves the communication within species. The positive feedback loop between the state-of-the-art level of intraspecific communication and its further evolution is formed. It seems that this feedback played a vital part in anthropogenesis.
Natural selection, norm of reaction, competition, population number, evolutionary stasis
Цит.: Severtsov A.S. Population ecology and progressive evolution // Moscow University Anthropology Bulletin (Vestnik Moskovskogo Universiteta. Seria XXIII. Antropologia), 2009; 4/2009; с. 5-14
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